Let's explain it in this way: Meaning: In "过了一会“, "过" means time passed by,like 5 minutes passed, whether you spend it or just sitting there doing nothing, time still passed; "一会" means a while, just a short time; After word meaning, it comes to the "Tense": In Chinese, the word "了" has a passed tense (or perfect tense) to show something "was" balabala, rather than "is", or someone "did" or "have done" something rather than "do" or "being to do". It's usually used when you describe something (you experienced, stories) to others. Like: I called tom last night but he's not in (say 9 clock). Then after a while (say 9:15) Tom called me back. Hope you can get the point there!! I called you twice on skype.... SOOOO, "过了一会" literally means after a little while.