At any moment of trading what does it mean when the market has more buyers than sellers?
Think of it as an infinitely large open apple market with no published prices, where there are vendors selling apples ("sellers") and patrons buying apples ("buyers"). So there are an infinite "number" of buyers and sellers. The apples are all completely identical, so there's no difference in buying from one vendor or another.
There are two types of both buyers and sellers - those that demand a certain price (price makers) and those that will buy/sell at any price (price takers). If there are more "buy takers", that means that the "sell makers" will set the price, which will go higher (since the sellers can set higher prices to their benefit. This happens until the price is high enough that there are enough "sell makers" to satisfy the "buy taker". At that point an"equilibrium" is reached and the price will stay at that level until additional "takers" from either the buy side or sell side want to buy/sell.
The list of "makers" is indicated in the order book that shows the bids and asks with associated volumes - as "takers" fill orders to satisfy the bids and asks, the p[rice rises and falls accordingly.
So yes, for each individual transaction there is one buyer and one seller, but there will me more "takers" on either the bid side or the ask side, which determines the "market" price.
Practically, the number of participants is not infinite, but there are typically "market makers" that ensure that there are enough buyers and sellers to keep the market flowing. Only in very extreme times are there a limited number of buyer and sellers.