I have an embarrassingly simple question. In a platform like NT, it is possible to have a candlestick chart based on Last, Bid, and Ask. I just realized that I did not really understand those concepts when I looked at the volume for each charts (Last, Bid, And Ask). The volumes for "Bid" and "Ask" are way more higher than the volume for Last. For example for ES 1min chart, Ask[vol] ~ 47k, Bid[vol]~ 41k, and Last[vol] ~ 506. I attach the picture here. I would appreciate if someone could explain in more details what volume in "Bid" and "Ask" mean here. Also what does "Last" really mean here? is it the last volume in the last tick(trade) or "what" of the bar? Thank you for your comments.

I'm not an expert but from my understanding: Ask volume is the total amount of contracts offered at the ask during the time frame. Bid volume is the total amount of contracts offered at the bid during the time frame. Last volume is the total amount of contacts traded during the time frame. Since not all contracts offered are traded, last volume will usually always be lower than ask or bid volume, with the temporary exception of when many market orders have been placed. If ask volume is significantly greater than bid volume, it indicates a likely downwards movement in price, and vice versa if bid volume is significantly greater than ask volume.

If anyone else knows a better answer or if I made a mistake please correct me.