idiot here, i have a question

im trying to understand what time is. ive been watching many videos on why nothing with mass can travel faster than the speed of light. and all of these people keep bringing up space-time and also separating space and time. what do they mean when they say time? how does mass travel through time? i always thought time was a human idea. or is that a different type of "time". not even sure if im asking this question in the right way but i really am trying my best to understand this