People seek out online therapy for many reasons. Studies have shown that it can just as effective as in person therapy for a variety of mental health conditions and treatment modalities, including CBT (Cognitive Behavior Therapy) which I use. Please not that online therapy is not appropriate for serious psychiatric illnesses.
Some people may choose online therapy simply because of geography; they don't live close to mental health services. Others may have mobility issues that make traveling to an office difficult (although my office is accessible). Many others choose online options because they are busy; cutting out the travel time from work or home can be a big advantage. Lastly, people are often just more comfortable in their own space, whether that's their home or office.
You may use any device (computer, tablet, smartphone) that has a strong internet connection. While my space is private, it is up to you to make sure your space can allow for confidentiality as well. Wired headphones can help as can making sure you are alone in your home, office, or car. I use a HIPAA compliant tele-health platform called Doxy.me. A secure video link will be email to you before your first appointment.
I do not use text-based therapy because so much is lost through that modality such as facial expressions. body language, and vocal signs. Phone sessions are an option but still not ideal for some of the same reasons. A therapist needs to be able to tune into a client's feelings/moods and this is much easier to do when sessions are face-to-face.
If you start with on-line therapy and decide that in-person might be a better fit, I do have an office on the west wide of Madison. If you start in person and decide that on-line might be a better fit, there is always the option to transition to that modality as well.