There are so many tattoo styles that it can be easy to get lost in definitions. What if you are looking for a specific style but you don't know how it is called? It happened to all of us. In a field where everyday there are new techniques, styles and tattoo shops are popping up in every corner we definitely need some clarity. And here it is. Feel free to add whatever you think is missing from the post in the comments below, there's always more to learn.
Old school, or old skool, or traditional refers to a Western (especially American) tattoo style. People didn't get tattooed in the Western world, and the only people who used to have contacts with tattooed people were sailors. South West Asi and Polynesia tribes have a strong tattoo culture, and they are often heavily tattoed: the very term "tattoo" comes from a Tahitian word ("ta-ttow", which is the onomatopeic sound of their traditional tattoo machine). That is exactly the reason why old school motifs are nautical: anchors, sailors, mermaids, nautical stars, boats, water, daggers, swallows, dices and also pinups and beautiful women.
Sailors often left their beloved girlfriends and wives on the land, so they had their portraits tattooed; they also were very superstitious and specific symbolic tattoos were used as "defense" against the odds of the sea.
Traditional tattoos are characterised by thick black or blue outlines and solid bright colors (red, yellow, green, blue). The result is a bold, big design that can sometimes look "rude" if compared with more advanced tattoo styles.
Traditional tattoo style was done by sailors, inmates and people without a tattoo artist diploma, and with a primitive tattoo equipment.
Today we have materials and tools, but the old school style is inspired by this traditional tattoos so it "traces" the same features. Western pomp is a cornerstone of these perfect little pin-ups.