@JustinXujia,
Wickets are lost when the bowler is able to get through the batter's defense and hit it, basically. There are 11 batters for each side, but, as two people are always up to bat at the same time, a side is out when ten wickets have fallen.
I'm not sure what a 20/20 match is?
Five wickets to spare means that Pakistan had only lost five wickets when it overtook india's score.
A batting collapse happens when a side is out for a very low score.