There are two development environments where you can interact with code on Quantopian: Research and the Algorithm IDE. The Environments section of the User Guide provides a walkthrough of the two environments, explaining many of the helpful features you can use while researching and developing a trading algorithm.

Research is a Jupyter notebook environment that is best suited for researching ideas. Research is the best place to query data, perform analyses, and build visualizations.
Algorithm IDE
The Algorithm IDE is where you can turn an idea from Research into a trading algorithm. The IDE is the only place to interact with the Algorithm API and allows you to backtest your trading algorithms.