Suppression a stun which you cannot cleanse out of. It is also unaffected by merc treads / any CC reductions, such as Irelia's passive. The only two ways to get out of it are either the caster gets interrupted or you use the active on quicksilver sash.
The suppression acts as a normal stun + locks all summoner spells (flash, cleanse)
The stun part of the suppression stops champions from using active skills (as of 16th Feb 2011), with the exceptions of:
Passive abilities will kick in, such as Anviva's egg.
Generally, each team has one jungler, which means that there will be one lane of two, and two lanes of one. Since the middle lane will always be a solo lane, this means that top and bottom will have varying numbers of champions, depending on the lane.
Top is usually considered a solo lane because the bottom lane is closer to Dragon, an important mid-game objective. Dragon is hard to solo for most non-junglers, and by keeping 2 champions in the bottom lane, it becomes quite viable to 3-man Dragon after a successful gank (or simply a double-kill). While top lane is closer to Baron Nashor, it takes quite a bit more effort to kill him - more than 3 champions in the early game can probably afford to put out. By the time Baron becomes available, the game is usually nearing the end of the laning phase, after which the difference between top and bottom lane is moot (because all 5 champions are roaming).
With a top solo lane, the champion has a leveling advantage and the potential to farm more minions (simply because there is no allied champion to compete with). Additionally, one must consider that if the other team does not have a jungler, they need to be able to successfully last 2 vs. 1. Most often, this means champions with good sustainability are better suited to the lane, such as Cho'goth, Mordekaiser, Vladimir, or Nasus.
Conversely, there are some champions who do not do well in a solo lane - these tend to be support champions like Soraka, Sona, or Janna who perform much better with a partner to buff/shield/heal. These champions usually go to the bottom lane to ensure that they are in a 2 vs. 2 situation.
In instances where there is no jungler on either team, both top and bottom will have an even number of champions. In this case you may be asked to "switch lanes" not because one lane is "better suited" than the other, but because switching lanes means changing which enemy champions you're fighting (and presumably, have been dying to).
Best Answer
Displacement effects (knock ups, knock backs, etc) are not affected by tenacity or any crowd control clearing effects like Cleanse or Quicksilver Sash. Displacements effects can be prevented by spell-shields however, like Banshees Veil and Morgana's Black Shield.
Suppression effects involve a channel by the caster and can only be stopped in one of three ways: