as said before - to make sure that they do not overlap

so for example:

starttime1: 3.00 endtime1: 4.00
starttime2: 4.01 endtime2: 5.12
starttime3: 3.23 endtime3: 3:59

in that example, starttime3 will collash - because starttime1 and endtime1 fit in that range.

Basically no time should interfere with any other time, making sure that each time is more or less than the previous time but certainly making sure that they do not collide with each other.

take for example your daily routine

you may have several meetings but you have to make sure that you do not have 2 meetings at 1 time but to make sure one proceeds the next....