Date is the day, month, and year of the concert. Venue is the place in which the concert took place. City is an inhabited place larger or more important than a town. Tickets Sold is how many tickets were sold for the concert. Capacity is how many people could fit into the venue, including really fat people.
Capacity deals with the capacity for that particular show, and it varies.
Maybe a certain venue was only selling a certain amount of seats, or the bands equipment or staging were taking up a section of seats. For example, the Universal Amphitheatre in LA says capacity for Sammy Hagar's show was 4,855, while capacity for Motley Crue at the same place was 6,179. Same place, different capacity. Kind of whacky, but it's all legit. Percent Full is what percentage the venue was full.