If you have a BulkSMS account, you can use the system to send SMS to individuals or a group of contacts.
It is easy to send an SMS directly to a contact, without having to use your cell phone, or try to manage cost claims around that. You can have up to three cell phone numbers per contact, which further simplifies sending. A typical use for a contact would be to send a birthday wish. For staff or volunteers it may be to send them a reminder about a current task.
This video shows sending an SMS to an individual.
If you are rather needing to send to an SMS to a group of contacts, you would use the Bulk SMS feature. This feature allows you include a first name merge field and will track deliverability statistics.