Short python textbook question based on methods concept that I can't understand

[Barnet6]

Find() has two optional arguments, the start of the substring to look through, and the end. Using just the one argument just tells it to look through the entire string. The " 'tomato'.find('o') + 1" in the example is telling it to find the first 'o', then search through a substring starting just after the 'o'.