What is 'freezing' a lane and how do you do it?

Freezing the lane means to hold the minions at a certain point in lane, normally closer to your tower allowing you to more safely farm because you are near a tower, and if are ahead, can deny your opponent CS and thus gold. It is done by simply last hitting minions while also stopping your opponent from hard pushing the minions all the way to tower.

If you are ahead and freeze the lane, it stifles the opponent and forces them into an awkward position. They can play up and risk being ganked, or put themselves in a spot to be killed by you alone if you are ahead, OR they can leave lane and give you more gold, exp, and cs then them and allow you to outscale item wise.

It means do your best to last hit the minions allowing, your minions to do as much possible damage to the enemy minions. This will "Freeze" the lane in place so you don't push towards their tower as hard.

Doing small things like waiting for a minions cast animation to start before killing the minion that your minion is attacking allows the enemy minions to actually deal more damage to yours and this can allow you to manipulate the wave to slow push towards your tower to allow for ganks.

This is important in every lane.

However in the top and bot lanes due to their length it is more important.

Freezing your lane is farming in a way that reduces their movement, so letting the minions do most of the damage without whittling their health down yourself, and autoing them when they're just about do die to reduce the movement down the lane by creeps.

Freezing your lane is something I recommend you wouldn't do, unless you are being camped or you cannot take the enemy turret. Definitely don't do after you lose your turret, because if the enemy is smart, he will rotate and take all your outer turrets.

It's basically an extremely selfish solo strat that people employ to try to get themselves ahead.

As it was said already below. Adding more to it, sometimes it's better to push if you know you can escape ganks then you can take some pressure of the enemy jungler from other lanes.

We, I at least, don't hear much or I don't see people talking about another minion-strategy a plat friend from school told me, which is making the wave push REALLY hard, later in the game.

You do this by not killing all enemy minions in a wave. Depending on the speed you want it to happen, or the size of the "charge" but leaving like, half enemy minions in relation to yours in a given lane, usually top or bot, will make your minions accumulate alot (a huge fkin wave) then, obviously, some enemy will have/want to go farm that, and now you can contest a better tower/dragon/baron in a 5v4. I've done it, it requires timing tho =P and team work to capitalize on it.

Imagine one of those huge waves pushing top, someone split-pushing bot and you making pressure/other objective. 2 of them will react to your team efforts to defend the turrets.

The less minions you leave in lane fighting yours, the faster it will push and less it will accumulate.

You try and hold a wave of minions at one certain point in the lane that is favorable to you, and you only last hit so the wave stays there as long as possible and does not go to your tower and reset or push out and put you in a spot where you might get ganked.

I could never do it because whenever I see that huge stack of minons i just feel the urge to waveclear all of them. I can't resist it.