You should know about Market, Limit, Stop, Stop-Limit, Trailing Stop, OCO, and OSO orders, how they are submitted, and how they are filled. Every order type is a tool for a specific use case. Understanding your tools is key to developing a good trading strategy and minimizing your losses.
Useful links to understand order types:
https://tradovate.zendesk.com/hc/en-us/articles/217733657-What-do-the-different-order-types-mean-