I'll see if I can clear it up for you a bit, although everyone has different terminology. There's some level of overlap, depending on scheme, but they usually differ some in alignment, size, athleticism, and primary responsibilities.
DE is usually a base defensive end, who may line up anywhere from 4i, 5 tech, or even wide 9 (although then we're more likely getting into EDGE territory). Generally they're bigger players who can be relied on as run stuffers. They may also reduce inside to 3 tech on primarily rushing down -- think Deatrich Wise, or a throwback in Jarvis Green, although he was more of a 34 DE playing the 4/5. In the draft, players like Chad Thomas, Rasheem Green, or Jalyn Holmes would be more pure DEs, and potentially players like Jullian Taylor or DaShawn Hand would be considered here as well, as 34 DEs.
EDGE is a catch-all for both 34 and 43 defenders who are QB head hunters (not literally; that's a flag these days). These are the guys who are paid big bucks to produce as pass rushers, although they vary from scheme to scheme. Von Miller and Demarcus Lawrence do different things, but both are EDGE players. In the draft, Bradley Chubb and Harold Landry are both considered EDGE players (with Chubb also falling into the DE category, and Landry potentially an OLB).
OLB can be either 34 or 43. We usually think of 34 OLB as EDGE players who stand up and occasionally drop into space (and depending on the type of scheme that may or may not be correct). In a 43, however, the OLB might have some rush ability, but they're not primarily an end of the line player who is moving forward on most snaps. They have more requirements in space, and are usually much smaller and faster than their 34 counterparts. For the draft, think of a Fred Warner, Skai Moore, Oren Burks, Uchenna Nwosu, or Peter Kalambayi -- some of these players could fit into either scheme, but they're not going to line up the same as one of the DEs I listed first.
This is a pretty rough breakdown, and probably misses a lot of nuance, but it might help you determine where analysts are coming from.
