Booleans

A boolean is a Lua value that is either true or false.

Additionally, Lua treats all values as if they're 'truthy' or 'falsey'.

If a value is truthy and it's in an if statement or a function that wants a boolean value, it's treated like it's true.

Example:

if 0 then
    log("truthy") -- numbers are truthy so this will always be logged
else
    log("falsey")
end

If a value is falsey and it's in an if statement or a function that wants a boolean value, it's treated like it's false.

Example:

if nil then
    log("truthy")
else
    log("falsey") -- nil is falsey so this will always be logged
end

The only values that are falsey are false and nil, every other value (numbers, tables, modelparts, etc) is truthy. (nil as a value means there's no information. It's literally nothing)

The not operator flips the truthiness of the value into true or false.

Examples (all of these are true statements):

not true == false
not false == true
not nil == true -- a non-boolean value is turned into a boolean
not models == false -- models is a modelpart and truthy, so flipping it turns it into false

When used in methods true usually activates something, and false deactivates it. However in some places returning true may turn something off, always read the description of a method, field, or event to discover what boolean does what.