I just played a round in the Duels Of The Planeswalkers PC Game. A LOT of wierd stuff happened and I don't know why. I had a character with lifelink. (4/4) In the combat phase I attacked the opponant. The opponant blocked with a 1/1. The encounter sent the 1/1 to the graveyard and I received 3 life, but my opponant did not take life damage.... How is that possible? (Sorry if this question is too vague... Like I said, A LOT of weird stuff happened and I have only been playing for a week so I may have some trouble articulating the scenario...)

In order for your creature to deal damage to the opponent when it is blocked it needs to have trample. Otherwise, the size of your creature doesn't really matter as it can be "chump" blocked by smaller creatures without dealing any damage to the opponent.

The biggest issue I'm seeing is that you only gained three life and not the requisite four. If you have a 4/4 lifelink and it's blocked by a 1/1, it technically still deals four damage to the opposing creature (even though one would kill it). As such, from the way you've described, the opposing creature should've been killed, you should've gained four life, and your opponent would've taken zero damage.

Does all of that make sense?