What is atomic mass, atomic number, isotopes and how are all these terms related to each other?

Atomic mass deals with the number of protons and neutrons added together, atomic number deals with protons only, though isotopes can be explained like this, say you had a hydrogen atom it's one proton and one electron if you add a neutron to it, the hydrogen becomes Deuterium which is a isotope of hydrogen it's the same atom just a neutron added to it for a different atomic mass if only slightly changed

Atomic mass is the sum of proton and neutrons

Atomic number is just number of protons

Isotopes of elements have same atomic number but different atomic mass due to difference in number of nuetrons