Think of punctuation as the traffic signs that guide your reader through your writing.
Without punctuation the reader has no idea when to stop and when to pause and if you’re about to change the subject from punctuation to grammar also the reader will get tired when reading great swaths of text without a chance to pause and breathe and contemplate what they’ve just read do you see what I mean?
Periods tell your reader when to stop, and commas let the reader know when it’s time to pause. There are other forms of punctuation like semi-colons, dashes, parenthesis, and brackets that can be useful too. But, let’s start with commas. If you work on using commas appropriately you will see an improvement in the clarity of your writing.
Click here for a link to a tutorial on commas from the Online Writing Lab at Purdue University.
https://owl.english.purdue.edu/owl/resource/692/01/