"A Buddha is someone who has realized the enlightenment that ends the cycle of birth and death and which brings liberation from suffering." In Sanskrit "Buddha" means an "awakened person". Then the people did the translation to English as an "Enlightened Person". The Buddha is also the person who is able to know the truth of life and death.
Most of the people recognise Siddartha Gautam as Buddha. But in fact he is one of many Buddhas they have already been to our planet. You can find here the list of Buddhas. But that is very possible there were many more who aren't listed. We can see on the quotes of Siddartha Gautam Buddha that a lot of Buddhas have been here and they will always be here but we have recognise them ourselves. Each and every human being in this planet have the capacity and ability to become Buddha if the person wants to wake up. That is obviously not an easy path but also not an impossible one.
There are many ways described by different Buddhas to wake up but we can see that quiet all of them have developed their way of meditation and they taught their disciples. Nowadays we can choose which suit better to us with our character. As they described the way of maditation varies on person to person.