The 1967 to 1973 Cougars were based on the second generation Mustangs, which actually looked a lot like the first generation Mustangs. The Cougar looked like neither 'Stang, and was most easily identified by its chrome comb grill and long horizontal taillights.
There were two models of the original Cougar: the base model and the XR7. The XR7 was a luxury model. Both of them also had a GT sports package available. The GT package included a 390 cubic inch FE series big block that replaced the 289 cubic inch small block in the base models. A convertible Cougar was first offered in 1969 and discontinued in 1973.
1971 saw a complete restyling of the Cougar. It was made to look bigger to fit in with the rest of the entry level luxury market. It was actually lighter than the original and only an inch longer, but the styling change made it look like a beast. The base engine was weak, but a 428 Cobra Jet was optional (and very rare).
From 1974 to 1979 the Cougar was made more upscale to fit in with a more intermediate luxury market. That meant the end of performance standards and the end of this car being liked by young car buyers. This car got bigger while others were getting smaller. In 1977 a station wagon Cougar was offered, and only for that year. It's a rare and odd model from this car line.
The 1980 to 1988 Cougars were based on the Ford Fox platform. Engines ranged from an I4 to a 302 cubic inch Windsor V8. Transmissions ranged from 3 or 4 speed automatics to a 5 speed manual.
The 1989 to 1997 Cougars were a complete overhaul from the previous models. Although the styling was boxy and boring, there was notable supercharged engine sold as an option with some of these cars.
These cars are all over the used car market. The first generation models are considered classics and are highly collected, but later generations are more likely to be found rotting away in a junk yard. Those that did survive are not bad cars, especially for a first-time car buyer. Try finding some good deals on eBay, especially on the classic models. There are also parts and even engines listed on there.