Range of second-level domain names to use
 

SEO is not the only factor to consider when doing a website, sometimes in order to meet the overall brand or marketing strategy, you have to use the second-level domain names, or when the site's content enough, the second-level domain names is sufficient to hold up a website, then the most good is better to use the second-level domain. For example, some companies have many series of products between some products are not too big, but the product is more than enough, this time on the need to enable the appropriate separate secondary domain name, and some site because there are a lot of different channels, each channel corresponding users are independent, then use the second-level domain is clearly more user-friendly, but also more conducive to the promotion

Secondary domain name than level directory good-looking, good mind, good writing and good communication.

Why should use secondary domain name forward, not directly pointing at?

From the point of view of SEO, if your level is not very high, USES the subdirectories than secondary domain name relative good point
Many virtual host does not support secondary domains pointing to

Those are best option if you want to target your audience in specific region such as UK, US, Europe, Australia, New Zeland.

SEO is not the only factor to consider when doing a website, sometimes in order to meet the overall brand or marketing strategy, you have to use the second-level domain names, or when the site's content enough, the second-level domain names is sufficient to hold up a website, Those are best option if you want to target your audience in specific region such as UK, US, Europe, Australia, New Zeland.