Inertia is when there is a change of speed or motion in an object. Like here, the football player is running with a football, but something is about to change.
The other football player tackles him and changes his motion by slowing him down and stopping him where he can't run anymore.
Friction-less is related to Newton's forst law by motion and change of direction just like inertia. Imagine you taking a step in the kitchen and then standing normally. If the ground has friction in it, then he will stay until another force is acted on it, but if the ground was friction-less he will move at the speed of him walking forever.