What is the difference between 'ser', and 'estar'?

(An Introduction to Ser/Estar)Ser is used to convey essential qualities. When you introduce yourself and talk about your name, your appearance, your nationality, your occupation and your relationships - these are all things which define you and your character and which have a certain permanence. 'Hola, yo soy Alex. Soy alto. Soy estudiante. Soy mexicano. Ese es mi padre. Mi padre es amable y chistoso.'('Hello, I am Alex. I am tall. I am a student. I am Mexican. That is my father. My father is kind and funny.').Use 'ser' for other permanent qualities, such as what an object is made of. A table is not temporarily made of wood - 'la mesa es de madera'. ('the table is wooden/(made) of wood'.).When you talk about the time, use 'ser' - 'Son las cinco. Hoy es viernes y ayer fue jueves.' ('It is 5 o'clock. Today is Friday and yesterday was Thursday.')Estar is used for temporary states and locations, to describe the way that you are currently feeling, the state of the weather etc. 'Estoy bien'. 'Estoy enfermo y cansado'. 'Estaba lloviendo'. 'Estamos de vacaciones'. ('I am well'. 'I am ill and tired'. 'It was raining'. 'We are on holiday'.)These are all temporary things..It is also used with verbs, adverbs and present and past participles in a way that 'ser' is not - you would say 'Estoy comiendo' ('I am eating') but never 'Soy comiendo', which is not grammatical and makes no sense in any case! Likewise 'Estoy leyendo un libro' ('I am reading a book') and never 'Soy leyendo un libro'.((NOTE! Bizarrely, because of this, we say 'estoy muerto' for 'I am dead', and not 'soy muerto', despite this being - in most cases - a fairly permanent condition! According to Spanish grammar it is an ongoing action and not a permanent state.))A particularly good example to illustrate this distinction would be 'Soy feliz' and 'Estoy feliz'. Both can be translated as 'I am happy', but this lacks nuance - simply by replacing 'estar' with 'ser', the entire meaning of the sentence changes radically:. 'Soy feliz' implies something permanent, an intrinsic characteristic. It means "I am a happy person". I may not even be particularly happy today, but in general and in essence, I am someone who can be defined as 'happy'.. 'Estoy feliz' implies something temporary, a current state and not a defining quality. It means: "I am happy", in the sense that "I am currently feeling happy". I am not saying anything about myself as a person, about my natural character etc. I am just happy right now.((The same goes for certain adjectives whose meaning changes completely based on which version of 'to be' they are used with - e.g.'Estamos listos' means 'We are ready', while 'Somos listos' means 'We are clever'. The implication is presumably that being permanently 'ready', as an essential quality, is a sign of being clever!))