In simple terms

 

You can think of it like this:

16.2 – Types of Treatment

What kind of treatment is being used?

• Psychotherapy
• Biomedical therapy
• Cognitive therapy
• Behaviour therapy
• CBT
• Psychodynamic approaches
• Humanistic approaches
• Medication
• ECT, etc.

16.3 – Treatment Modalities

How is the therapy delivered?

For example:

• Individual therapy – one person works with a therapist.
• Group therapy – several people work together with a therapist.
• Couples therapy – partners work together on relationship difficulties.
• Family therapy – family members work together to address problems affecting the family.
• Self-help/support approaches – people may also receive support through structured groups or other resources.

A really simple distinction

I'd explain it in your book this way:

Types of therapy tell us WHAT treatment is being used.

Treatment modalities tell us HOW the treatment is provided.

For example, CBT is a type of therapy, while individual CBT or group CBT describes the modality in which it is delivered.

That's a useful distinction because otherwise someone reading the material could easily think that individual therapy, group therapy, and family therapy are completely different psychological theories. They aren't necessarily — they're different ways of providing treatment.

And this could fit nicely into your book as a small section:

Treatment = What is being done?
Modality = Who is involved and how is it delivered?
Therapeutic approach = What psychological theory or method guides it?