If statements can have three components. First is
if condition
statement
statement
end
The parser gets the if symbol, skips it, and expects a <condition> to follow. After that comes a sequence of statements, and if at any time an end is seen, then the statement is complete.
However, if the parser sees an elseif symbol before it sees the end, it begins to parse the elseif section of the if statement. Elseif is basically the same as the if statement:
elseif condition
statement
statement
end
There could be multiple elseif parts. Again, if the parser sees an else symbol before it sees the end, then it starts parsing the else:
else
statement
statement
end
This is just the else symbol followed by some more statements. The end must terminate the if statement after an else.
Source: Parker James R. (2021), Python: An Introduction to Programming, Mercury Learning and Information; Second edition.