I wouldn't worry too much about it

. For the basics they offer an Instant Mail package that would, if you wanted it, allow up to five totally different email addresses each with a 2 GB sized mail box. In your case, initially at least

, you would only need one.
However, what you can do is create aliases. These are email addresses with the same domain name but different beginnings. e.g.
your main address might be
[email protected]
but you could then create aliases such as
'different beginning used for particular web sites or services'@jelly-tussle.co.uk
'even another different beginning used for another particular web sites or services'@jelly-tussle.co.uk
etc. You can have up to 150 of these aliases per main email address. These are useful if you want to keep different services/sites apart for easy filtering or or to keep track of whether some of the services/sites you use which ask for an email address to use them are giving out your email addresses to SPAMmers and the like. But for your needs for now the basic package is all you need to worry about.
Catchall means that any email with an ending of your domain, i.e. the jelly-tussle.co.uk part in the above example, but with any beginning part would be caught for your later perusal. Though where you haven't created an address with a particular alias it is more likely than not that such emails are SPAM.
Other providers offer similar features in their mail packages at roughly the same sort of price.