This Ted-Ed video 'What is dyslexia?' by Kelli Sandman-Hurley is a good introduction to dyslexia.
Dyslexia is a life long, usually genetic, inherited condition and affects around 10 per cent of the population. It is a specific learning difficulty, or difference (SpLD). Although there is often the assumption that dyslexia may just affect reading and writing skills, it's actually about information processing: dyslexic people may have difficulty processing and remembering information they see and hear. This can affect learning and the acquisition of literacy skills.
Dyslexia can also impact on other areas such as memory and organisational skills. It is no indication of intelligence.
As each person is unique, so is everyone's experience of dyslexia. It can range from mild to severe, and it can co-occur with other learning differences.
It is important to remember that there are positives to thinking differently. Many dyslexic people show strengths in areas such as reasoning and in visual and creative fields.