Aliases on Blockmarket Desktop can be thought of as Syscoin Accounts. It is necessary to have one before using any of the features in Blockmarket.
You can have multiple aliases in the same wallet; for example, you might have one for one business use and one for home use.

Aliases eliminate the need to remember the long Syscoin address, hence use of the name 'alias'.
Aliases are somewhat similar to domains on the internet. Only one person can own an alias and currently cannot be transferred to other users at this time.

Note: Creating a new alias will cost a small transaction fee. Increasing the expiration date will incur a much larger fee. It is recommended to start with a 1 year expiry date.