A sliding tile is any of the three types of tiles that normally make an object move at 10 m/s: force floors, ice and teleports. They have special properties when interacting with these objects which differ between the two sets.
MS[]
Sliding tiles in MS always slide objects at 10 m/s, unless Chip is stepping with the appropriate boot. Even though blobs and teeth move at a mere 2.5 m/s on any non-sliding tile, they still quadruple to 10 m/s.
Boosting is a result of passing over sliding tiles. Chip's Challenge allows only one voluntary move every turn; this does happen, but since the voluntary move is still within the same turn as the last sliding tile, it can be performed immediately after the last involuntary move - and if that voluntary move ended a turn, a spring slide can be used, adding yet another extra move. Consequently, a spring slide can be used any time Chip exits a teleport.
Lynx[]
In Lynx, blobs actually do move at 5 m/s on sliding tiles, which is double their speed: since blobs actually move at 5 m/s when moving and 0 m/s when not - only averaging 2.5 m/s - their involuntary speed is fixed at 5 m/s.