The 80186 was mainly used in embedded products. It's not very different to a 8086. It just had a few changes. I think very few personal computers bundled a 80186.
For the trivia, there're lots of 8086s and 80186s in the NASA Shuttles.
For the record, those are the most common Intel processors:
4004 was a 4 bits processor running at 100 Khz. It happened to be the first complete CPU on a single chip, released in 1974.
8008 was a 8 bits processor. The famous Z80 is heavily based on this one, yet cheaper and with a double instruction set. Other than that, they are practically compatible.
8086 came in 1978 as a powerful 16 bits processor with 20 bits of address space, meaning that it could handle up to 1 meg!! WHOAH!! (well, at least in 1978 1 meg looked like Sci-fi). It was used in expensive PCs.
8088 came around 1980 and was the de-facto processor IBM used in their first PCs. It's some kind of stripped-down 8086. Basicly it's a 8086 but with an external data bus of 8 bits. It made posible to build computers with cheaper 8 bits devices. That made PCs affordable for many more people.
80186s were used in embedded systems.
80286s came in 1984 and featured an incredible 24 bits address space, i.e. capable to use 16 megs of memory. Extended memory models began to be used. It was very expensive and wasn't used on home PCs until later.
80386s came in 1986. They were the first 32 bits processors by Intel.
80486 came later with incredible added features such as pipelining and much bigger caches.
80586s are Pentiums and Pentium MMXs, 80686s are Pentium Pros and Penitum II.
After that, I dunno if they kept the numeration.
