Value betting has nothing to do with bet size, or board texture, or anything like that. It's simply betting because you think it is likely you have the best hand. If you do think it probable you have the best hand, you sell it for what it's worth. If you thought villain will call an all in, you might do that, if you think he'll only call a 1/5 pot bet, then that's what you do. They're both value bets, just different sizes of them.
A lot of people don't understand how to size bets either because they're so results oriented. Don't fall into this trap. People don't push the nuts or hands close to the nuts hard enough often enough. They get so focused on what happens right now, and not what will happen over thousands of trials. Here's what I mean, say the river's out, you have the nuts. You have effective stacks left of 130bb's heads up and you're first to act.
You raised preflop to 3bb's and got one call. Bet 4bb on flop, called. Bet 1/2 pot on turn, called. The pot is now 28bb's on the river.
You reason that if you shove, villain will only call 15% of the time, folding a full 85%.
If you bet pot, villain will call 65% fold 35%
If you bet =<1/2 pot, villain will call 90% fold 10%
Which bet is most profitable?
Shoving here, even though it's hardly ever called is the best play!
EV=(%call)*(Size bet)
Shove = (.15) * (130) = 19.5bb's
Psb = (.65) * (28) = 18.2bb's
1/2 psb=(.90) * (14) = 12.6bb's
The main thing I want you to see is that these are ALL value bets. I'm not trying to tell you shove every river, but that a shove is just as much a value bet as a 1/2 pot bet, with a specific value that you can roughly determine.