Crochet patterns come in two flavors: written and charts. Complex patterns can be represented using standard abbreviations or symbols.
The written pattern for a row of this baby blanket looks like this:
"*hdc, 3sc, hdc, 3dc* repeat from * to end of row," which means, "1 half-double crochet, 3 single crochet, 1 half-double crochet, 3 double crochet. Repeat this set of stitches to the end of the row."
Here are some great places to find patterns and tutorials online:
https://www.ravelry.com/account/login
https://www.yarnspirations.com/
These standardized symbols are usually used in American charts:
350+ Crochet Tips, Techniques, and Trade Secrets by 
Complete Crochet Course by