Yup they're tied together but they aren't the same thing.
Hooke's law states that the extension/compression of a spring is directly proportional to the force exerted upon it.
For example, if you have a spring and when you pull it with a force of 10N it extends by 1cm, you can expect it to extend by 2cm when you pull it with a force of 20N.
Spring constant also known as force constant is a measure of the elasticity of the spring. The higher its value, the more the force you will need to exert to extend the spring.
For example, a short spring has a higher spring constant that a long spring if the other aspects of it are the same (thickness, material). If it takes you 10N to extend the short spring by 1cm, to extend the long spring by the same amount, it would take less force, perhaps 5N.
Hooke's law is incorrect when you extend a spring pass its elastic limit. The elastic limit is the maximum extension the spring can withstand to return to its equilibrium position. Extending it any further than this point and the spring will be broken. Further extensions when the spring is broken do not obey Hooke's law.
The spring constant is not invented but actually just used to relate the force exerted on the spring to its extension.