Query in Syntax

Hello All,

Can someone please help me understand the following:

In the variable section, we see the first variable is assigned without any round bracket or $ sign like this
mission_name=lunar-mission

However when we wanted store the result of another command, round brackets are used like this
rocket_status$(rocket-status $mission_name)

We use “=” to assign a value to a variable then we used “$” to call the value itself.