Redis is a simple, persistent, incredibly fast data storage system. It is easy to install, easy to work with and supports lots of languages.
Redis is well documented and you would do well to read various publications, like The Little Redis Book, by Karl Sedgwin.
What? Redis is a superb database that can be used with a number languages.
Why? Very fast, simple and fun. For me, it is the most enjoyable data storage system of the 'NoSQL' family.
Would you? Oh God, yes! It's easy to install and fits 'my mindset'.
Because of its nature, Redis is used for things like Memcaching and quite often sits alongside MySQL. In many ways, I think this is a shame. For me, storage engines like Redis or Riak, will never gain popular acceptance if they are only used for niche projects. This is not to say that it is the best for every situation, but I personally see no reason why you can't use something like Redis in a CRUD application. Why not? It's a storage engine, it's fast and it's easy/quick to implement and it is more fun.
I am sure there are many that will disagree with me on this... but they probably haven't kissed a girl. I have (and yes, she was conscious - promise)!
Redis can be installed on your server. However, there may be many who use shared hosting and will probably not be allowed to install additional packages on them.
Luckily, there are alternatives. Companies like Redis4You allow users to store their data on their servers. Packages start at free for a few megs (that is enough to store a decent-sized website) and charge for more space.
This documentation will be using Redis4You, but it should be easy to adapt the code if you have your own installation or use another host company.
Although simple, Redis does an awful lot more than I will cover. I will be showing simple, practical ideas, that should be enough for you to build on.
These examples will be written in PHP and Predis: a Flexible and feature-complete PHP client library for Redis.