On 7 May, many people all over the world will be marking World Asthma Day.
This is a global event that happens every year, which is organised to help people to better understand asthma and how we look after people who have the condition.
Asthma is a long-term condition - also known as a chronic one - which affects the lungs and the way that we breathe.
It's known as 'chronic' because of its long-lasting effects and is the most common chronic condition among children.
Asthma can cause wheezing, breathlessness, the chest feeling tight and coughing.
At its worst, it can cause a person to have an asthmatic attack.
This happens when tubes carrying oxygen to lungs get narrow and inflamed, making it difficult to breathe.
Asthma attacks can be triggered by different things - for example pollen, dust, pet hair, mould or pollution.
According to Asthma UK, around 5.4 million people in the UK are currently being treated for asthma.
That's one in every 12 adults and one in every 11 children.
Asthma affects more boys than girls.
Scientists do not know exactly what causes asthma, although they believe that some aspects of the way we live could affect it - eg how good the air circulation is in our modern homes and how much we are exposed to fumes.
You cannot catch it from another person.
However, it does tend to run in families, especially if there's a history of allergies.
Asthma cannot be cured, but with the right treatment and managed properly, it can be controlled to prevent patients from having asthma attacks or reduce the number that they may have.
Treatment might include using a special inhaler or taking daily medicine.
Inhalers are used so people with asthma can breathe in the medicine so that it reaches their lungs quickly and starts to make them better.
Patients may also learn the sort of triggers that can cause an attack and try to avoid those things.