You must register your book with bibliographic data providers. The modern book trade likes to do things by automation: Book information is aggregated by data providers and made available to companies in the trade, including online retailers. These book records are either sold or given freely, it varies by market. Booksellers decide how often to update their websites, catalogues, and shop computer systems with the data. Thousands of bookshops and websites are then able to have up-to-date information about your book, without having to deal with thousands of publishers and tens of thousands of authors on a daily basis.
Getting book information to the bibliographic data providers and keeping it up-to-date (for example, adding rave reviews obtained after publication) is important and requires some work. And just to make matters slightly more complicated there are of course exceptions to the rule, and each company uses data differently.
Normally a publisher’s task, this can be done by self-publishers too. For example, the UK data provider Nielsen Book allows publishers to submit basic book details via an online service for free. However, the free service does not allow for including essential items such as: a long description; reviews; table of contents; author biographies; awards; or promotional details.
In order to give your book the best chance of success it is important that rich, full bibliographic data is made available to the trade.