Smallish bits of content that don't have an independent existence on the site (e.g. they're not node content summaries) get put into custom blocks.
These are accessible under Structure -> Block layout -> Custom block library.
Custom blocks without much structure have been created as "Basic" type blocks, and other more complex blocks are created as one of the custom block types, i.e. "Did you know" or "Download or Link", or "Mini Carousel", etc.
Most of these are fairly easy to figure out when you're editing them, the only one that's a little complicated is the "Funding Cycle" block which pulls in information about the current funding cycle. See below ...