An atheist is someone who believes there is no God.
A secularist, on the other hand, whether they believe in God or not,
believe that religion should not interfere in the running of the state.
The National Secular Society was founded back in the 19th century,
but the concept of secularism,
and religion not interfering in the state and people of all religions and none being equal,
has been around since time immemorial.
You can have a religious secularist.
You can have someone who believes in God but does not try to abuse the apparatus of state
to force their beliefs on other people,
to discriminate against people who don't hold their beliefs,
or to force their religious lifestyle on other people.
Young people are becoming more impacted by secular issues
and becoming more aware and interested in them.
Nowadays, the huge idealogical difference in the world is about religion;
about those that believe that religion should run the state,
those who believe that they have the right to impose their religion on others,
and those who believe religion is a personal thing and want to keep the state free of religion.
If I was to sum up secularism in one word, I would say it's about equality.
History has shown that where religion has run the state,
people have not been equal.