Hypertext provides a simple implementation of progressive disclosure:
higher-level pages contain higher-level concepts and simplified
descriptions, and lower-level pages fill in the details for those users
who want to know everything.

In a system designed
with progressive disclosure, the very fact that something appears on
the initial display tells users that it’s important.

For novice users, this helps prioritize their
attention so that they only spend time on features that are most likely
to be useful to them. By hiding the advanced settings, progressive
disclosure helps novice users avoid mistakes and saves them the time
they would have spent contemplating features that they don’t need.

For advanced users, the smaller initial
display also saves them time because they avoid having to scan past a
large list of features they rarely use.

Progressive disclosure thus improves three of usability’s five components: learnability, efficiency of use, and error rate.

You might assume that by initially focusing users’ attention on
a few core features, they might build a limiting mental model of the
system and thus be unable to understand all of their options. Research says that these are groundless worries: people understand a system better when you help them prioritize features and spend more time on the most important ones.