The difference?!

Ashley • I`m Ashley. My husband and I have been married for 6 years and together for 9. We have two beautiful girls and an angel.
Good afternoon!! 
Could someone please explain the difference between evaps and indents? I didn't know these existed until using this app. I've peed on so many tests I can spot the faintest of lines a mile away, but I'm still confused about those two terms. Evaps aren't supposed to have any color, right? I either have three wicked evaps, indents, or faint BFPs. Pure confusion has set in :) 
Thanks for the help!