An edge is a line segment that joins two vertices. More on point to your question, in context, an edge is an advantage over the markets or other traders. It is what makes you a profitable trader. The difficult part is finding an edge, creating a plan and trading the plan (read your edge). An edge could be anything, from a trading methodology to an algorithm.
The Vital Importance Of Defining Your Trading Edge (IYR) https://www.investopedia.com/articl...tal-importance-defining-your-trading-edge.asp
An edge comes from a process you have, to place a bet on an occurrence where you have a higher probability of success than loss. For Blackjack, it is card counting. For trading, it can be anything that works consistently. Most "retail" day traders find this with some type of charting technique. Most banks and institutional find unique data sets to exploit. Bob
Edge=advantage similar: having a "card up your sleeve" or "Bob's your uncle" In the latter case we are not referring to Mr. Morse, though having him as your uncle would probably be a bonus.
to simplify: some reason why you think you could, via your trading and what not, beat just sticking your money in SPY, QQQ, etc.
An edge is a combination of different things that come together to achieve a common goal.. That's why success is hard at first in this world, because you have to master emotions, execution, risk and a lot more. An edge is "Mastery".. It is not a thing, it's a PROCESS.