Sundays are the main NFL day during the week!
On Sundays, the NFL games start at 1:00 Eastern and 4:15 Eastern. Most teams play at 1:00 with only a few "late games" at 4:00.
Most Sundays, there is also a night game - I think that starts at 8:30 Eastern. It's neat because later in the season, the Sunday night teams are re-evaluated as the game approaches - so we all don't get stuck watching some meaningless (in terms of playoffs) or bad (2 loser teams against each other) game.
Then, there's Monday night games on ESPN. It's always a big honor for teams to play on Monday nights - it means their games were interesting or they played well the previous year. Not every team will get to play on Monday night and some teams get to play more than a fair share of Monday night games.
This Monday, they are having 2 games - one at 7:00 and one at 10:30 Eastern. Don't worry - the 10:30 one is the Chargers and the Raiders and probably isn't worth staying up to watch.
The NFL also mixes in Thursday night games - but these aren't every week, so it's hard to keep track of them.