What's the difference between ser and estar?

Both ser and estar mean ‘to be’ but each has different uses. This can be confusing for native English speakers because in English there is only one word. Ser is used when we want to describe characteristics that are permanent or unchanging, for example ‘el perro es negro’. It’s also used for nationalities for example ‘soy inglesa’. Professions and religions also use ser for example ‘son profesores’ and ‘somos musulmanes’. On the other hand, we use estar when we want to describe something temporary such as feelings or locations, for example ‘estoy cansada’, because you might not be tired later and ‘estoy en casa’ because we assume that you won’t be in your house forever. Estar is also used for the present progressive e.g. ‘estoy caminando a la escuela’ to express that you are doing something right now.
The difference between ser and estar can also be confusing because there are some exceptions. For instance time, which obviously changes from one second to the next, uses ser. This is because the concept of time always exists. Another confusing example is the concept of death, which uses estar because of the idea of reincarnation. Similarly, you might ask why professions are considered unchanging and therefore use ser, because lots of people change jobs. Whilst this is true nowadays, in the past most people used to have one profession throughout their life and the Spanish language still reflects this. Though it might seem confusing at first, once you get a grasp of the rules it’ll become much easier to put them into practice.