Font license, Desktop or Web or both?

I’m an artist using Blocs to create my own website and I’m a little perplexed about font licensing.

I’m thinking about buying two fonts both from the same foundry.
They’ll only be used within the Blocs software to create and then publish my website.
Do I need both a desktop licence and a web license or both?

It’s pretty clear to me what a web license is but I’m a little vague as to what a desktop license is and if I need one as well as the web license in this particular scenario.

Thanks in advance for any help.

Mozz