Search volume is how many times a keyword is searched on average each month, usually for one country. Tools estimate it from search engine data, so treat it as a guide, not an exact count.
Why it matters
It shows demand. A keyword searched 2,400 times a month can bring far more visitors than one searched 20 times, if you rank well for it.
Example
"Coffee subscription for beginners" might show 2,400 searches a month and "single origin vs blend" 390. Both can be worth writing about: the smaller one may be easier to rank for and closer to a sale.
What to do
Don't chase volume alone. Weigh it against how relevant the keyword is to your business and how hard it is to rank for. A run of smaller, relevant keywords often beats one big, competitive one.