A weblog is very simply an online journal that is crawled and indexed much like a website. As with an online newsletter a blog can be tailored to match a specific corporate image and composed to promote a product or service. Blogs also have the benefit of increasing links back to your official website.
The main difference between a blog and an online newsletter is that blogs are not emailed to subscribers but appear on search results as any normal website. In terms of time commitment, blogs generally contain shorter articles than newsletters but are updated daily.
They offer all the same benefits as an online newsletters except that blogs are not posted directly to subscribers. Blogs generally rank well in search results as they regarded as news sites. This does means that a blog has to be updated regularly in order to maintain a good position.