It's a trading platform by TD Ameritrade. It exists as a mobile app, desktop app, and web app. I find the website to be the most convenient to use.
https://www.tdameritrade.com/tools-and-platforms/thinkorswim.page
ThinkOrSwim is just the name of TDAmeritrade’s active trader platform. You login to it with your TDA credentials and it offers everything that the normal platform does with additional tools and a layout which can be better for active or sophisticated trading. I actually like the different views better for different information, so I will often be logged into both the standard and TOS platform simultaneously. It has also been confirmed that the TOS platform will be continued through the TDA/Schwab merger and will eventually be available to current Schwab clients as well. I have found the margin capabilities of TDA to be very good.
https://www.tdameritrade.com/tools-and-platforms/thinkorswim.page
https://www.tdameritrade.com/tools-and-platforms/thinkorswim.page
It's a tool you get access to with tdameritrade. I used the paper account feature and the thinkback feature to do lots of testing and general playing around until I started doing real options trading with my own money.
And no lessons or anything needed to do options trading. It might be a little before you can get approved though, due to all that has happened in the past few weeks. They just ask you a few questions about your intent for trading and what experience you have, etc. I straight up said I had no experience and that I was trading to make some supplimental income or something like that and they gave me like tier 3 trading access or something.
https://www.tdameritrade.com/tools-and-platforms/thinkorswim.page
Thinkorswim is TD’s trading platform. It’s where you’ll be doing most if not all of your trading. You can also do simulated trading (TD calls it papertrading) where you can practice making trades with fake money.
I’d recommend taking a few weeks to get familiar with the platform, learn how order types and executions work, learn some technical analysis (charts and indicators) and see if you can turn a profit papertrading.
Keep in mind though most of your learning experience will be seen when you start trading live, so get comfortable enough, start small, and jump in.