As per Wikipedia:
SnapLogic is a commercial software company that provides Integration Platform as a Service (iPaaS) tools for connecting Cloud data sources, SaaS applications and on-premises business software applications.
It is surely a competitor to informatica, but it doesn't seem to be just another ETL tool. I have a rough understanding that it is used for data integration but that's about it.
Is it merely an ETL tool or does it have any other functionality? Also, what are iPaaS tools in general?
Well, the best place to learn about SnapLogic will be their website, https://www.snaplogic.com/
Here is a video of SnapLogic: https://www.youtube.com/watch?v=KYJK7bjOlA0
A simple developer friendly example: Let's say i want to search for twitter feeds posted with a particular hashtag by a particular person and write that data into a database of my choice or into amazon S3. SnapLogic allows me to do that without learning about the Twitter API and AWS. SnapLogic takes care of the abstraction for the user so that they can focus on the business logic of things.
The demos are available in the blog: http://www.snaplogic.com/blog
A look at SnapLogic on crunchbase is not a bad idea and you could also find their competitors there.
Your other questions like what are integration platform as a service(iPaaS) tools is too basic and should just be googled. Basically there are two types of cloud integration, iPaaS and dPaaS