Ok, assuming you meant virtual sexual encounter, here it goes....
Obviously since there is no physical contact, what players are doing in SL is giving each other a "mind fuck". How enjoyable it is depends on how prepared you are.
When you first get into Second Life your avatar is fairly limited. You receive a basic skin, clothes and no sexual parts. So if you are willing to take the time and invest some money (maybe $20 at most) you can go virtual shopping and purchase a better looking avatar skin, nice virtual clothes and a set of sexual equipment. (animated penis for males and vaginas for females) If you ever wondered what it would be like to be a female, now is your chance. You can even get a virtual boob job and get yourself a huge bust line. (boobs that grow and shrink as well as drip/spray milk)
Ok, so you've purchased a hot looking male avatar skin, you've purchased cool clothes & shoes/boots and you've even purchased the best available penis that grows into an erection and cums on command. So where do I go to hook up with some hot looking virtual women? Hold on! Once you find your hot tail, where are you going to take her?
Planning ahead, you search Second life for a location with a nice private room equiped with a "sex bed" complete with sexual animations for you to use. mmmm...but most of those freebie sex beds are in public places where others might come by and see you. Better yet, you decide to rent your own virtual place which might be a castle, an apartment or whatever you like for your sexual lair. You even go out and purchase the best sex bed that money can buy complete with several dozen poses for you to use with your partner. (Poses like hug, kiss, eat her, suck him, doggy, split her, spank her, etc.) So now you have a place to take her, but where do you find a willing player?
Second Life is full of clubs, dance halls, bars, fetish sites, bdsm dungeons, etc where you can find other players of the opposite sex that have the same ideas you have. So....you do a search and find a place that looks promising. You teleport to the location and walk in...
Well depending on what time of the day you decide to begin your hunt, you may find Second Life a lonely place. Weekday nights are quiet, but Fridays and Saturday are usually busy. (gee, just like real life!) So you do a search on events in SL and discover any number of virtual parties going on. You pick one and teleport to it.
You manuever your handsome avatar into the dance hall and gawk at all the hot sexy looking avatars in the room. Really, you have to see it to believe it. Everyone in SL looks hot and sexy. It's hard to find a plain, over weight or ugly looking avatar. So finding some nice eye candy is not going to be hard at all. So now you get your avatar dancing on the virtual dance floor and start checking out all the lovely gals.
Using your computer mouse, you can click on other players avatars and check out their profiles. This is extremely helpful information. Smart players will type up a very detailed description of who they are, what they like and what their limits are. This saves you a lot of wasted time going after someone who is only there to do some virtual dancing and not virtual sex. You can eliminate those players who don't speak your language (there are a lot of german, french, japanese players in SL), whose who have nothing in their profile (probably new, a "noobie"), whose who have a fetish or kink that doesn't appeal to you (things like scat, torture, rape, vore, etc.) or players who don't want to have sex with males. (There seems to be a lot of lesbians in SL or maybe they are males who are playing female avatars)
After dancing around a bit, you read one female profile that really catches your interest. So you contact her by sending an Individual Message (IM) to her. Just like real life, you will have to have some communication skills to get her interested and keep talking to you. But just like real life, you strike out. not to fear, you decide a virtual hooker is the way to do.
So you do a search and find a location that has a virtual red light district. You teleport there and immediately spot several hot looking female avatars who are obviously selling their sexual wares. Unlike the club scene, these lovely ladies greet you immediately. You will probably receive severals IMs at once offering to give you what you want. (Hi honey, looking for a BJ? Tammy will treat you real good!!) You smile to yourself as you pick out the female avatar that you find the most attractive and engages you with a conversation that really gets you excited.
Now it's just a matter of negotiation. Do you want a half hour, hour? One gal, two? How much do you have honey? Your place or mine? (You get the idea) Finally, you settle on the time and what you want. She teleports you to her own secluded place. Perhaps a treehouse in a virtual forest with a huge virtual bed sitting high up in the branches. A well prepared "hostess" will do some sexy dancing for you to get you in the mood. Then slowly perform a virtual strip. After that you hop into her big bed and you begin working your way through a series of sexual poses that twist and turn your avatars in all manner of positions.
Then you discover is not so easy to give yourself a handjob with one hand while the other types your responses. Hopefully she will do most of the talking and let you watch as she moves both her own and your avatar into different positions. Keeping an eye on the clock, you remember to have your virtual penis cum as you climax in SL (and maybe RL as well.)
Your avatar sprays a long jet of virtual cum and you sit back to enjoy the after glow. After a little small talk, your lady friend quickly exits. You decide to stick around and have your avatar pull out a virtual cigarette to cap off the encounter.
Maybe next time you can find a female avatar who doesn't do it for the money. So you put your virtual clothes back on and head out to another SL party and continue your virtual beaver hunt.......
Well, that is my tongue-in-cheek contribution. It's a fairly generic encounter, but fits what most players would encounter if you decide to try out Second Life.