I’ll explain any jargon in the future!
Synthesising is basically taking a look at any research, what insights we can take it from it, and then making it actionable in the design. A note about research. Sometimes I can interview someone for 30 minutes and not come away with anything, or we do some card sorting it ends up looking like what we would have done anyway. Another issue is a user might say something, but act contrary to that. So it’s just a balance of qualitative and quantitative research and understanding the limits.
A persona is where we take any research insights and create a mock user to keep us a grounded to the user needs and possible pain points (hurdles the user faces when engaging with the environment, in this case a website). The issue with personas it that they can be misapplied. For instance, listing demographic information and how they love their cat might remind me that we’re dealing with real people here but it doesn’t tell me much about they will behave etc. To get that info enough research needs to be done, or we’re forced to make assumptions. Assumptions can be okay if they’re reasonably grounded, like expert vs. novice users.
Card sorting is to help with the info/menu structure. It’s basically asking users “here are five menu headings, and if you wanted to see where other users are in your area, which menu would you find that under?” It’s to get a sense of users expectations and take a look into their mental model (their cognitive map of how something should work). Honestly, the value of card sorting scales with the complexity of the website in my opinion, so it’s not always needed.