After methods are defined, can someone explain how code is read and what is happening in each step?

So, these are variables and they are assigned data from the return of the function.

The first one:

name = get_name()

runs the get_name method. That asks for your name and returns a string based on your input. This string is what gets assigned to the variable "name"

That variable is used in the next call

greet(name)

it would be the same as if you called the function like:

greet("Rob")

name is a string and you call the greet function with the variable that has a string as the value.

number = get_number()

is the same as get_name(), except the ".to_i" sends an integer value to the variable "number".

the final statement:

if divisible_by_3?(number)

will call the function. If you look at the function, it returns either true or false. so it could be read: if "true" do the inside block. If "false" do nothing.