After I turn on the bot, does it start trading immediately?

It depends on your settings. If you don’t have any signals or filters, it will enter the market within a minute. In case you do have one or many filters, a signal bot will enter the market only when all conditions are met.

No filters - high deal frequency but more risk, as there is no market analysis.

One or several filters - more reliable trades as special programs are monitoring the market and allow bot to trade only when the market goes in your favour, but usually less deal frequency.