We are spoiled by our grocery stores (also manipulated and taken advantage of in a major way but that’s a topic for a different day…). Anywaaaayyyy, you can walk into most mainstream grocery chains anywhere in America and find berries, tomatoes, corn on the cob, and asparagus almost any time of year. These foods are flown into our stores or driven across the country all so we can have access to whatever produce our hearts' desire. In contrast, if you go to a local farmer's market in Tennessee in December, it's going to slim pickings when it comes to things that aren't green or root vegetables. That's because food is seasonal - dependent on geographical location and weather.
When we eat seasonally, that means we're consuming food that is purchased around the same time it's harvested (on "in season") and there are so many advantages to eating this way - better taste, more nutritious, generally less expensive, and likely a cleaner (and many times organic) product. While I know it's not realistic to ask everyone to eat only food that is in season in their geographic location all the time (although how rad would that be if it was possible), I do think it's important to at least be aware of what is in season so you can choose those foods more often.
You'll also notice that as the seasons change, the foods I reach for again and again change as well - i.e. I know you were seeing A LOT of asparagus on my meal plans in May. Below is a look at what's in season here in Tennessee right now. If you'd like a full list or live elsewhere and want to take a look at what's in season where you live, The Seasonal Food Guide is a great online resource.