To identify the variables you can use in your Email Templates and through your website, you can navigate to Emails - Email Templates You can find the list here:
Special Note Regarding Variable Names
With the following information about SEO variables set, there is another point that needs to be made regarding SEO variable names. You will need to avoid naming a SEO variable name the same as a column on the database. For example, the following is a list of columns names found in the database that you should not use as SEO variable names:
type, old_filename, new_filename, updated_by, name, icon, keywords, order, group_name, database, first_name, last_name, email, company, phone_number, fax_number, address1, address2, zip_code, zip, state_code, country_code, state_ln, country_ln, website, twitter, facebook, linkedin, blog, active, token, position, profession, additional, link, link_order, user_id, comments, data_name, data_type, form, form_name, search_results, h1, h2, post_type, widget, widget_name, status, title, section, filename, quote, experience, affiliation, awards, published, education, softwares, fees, about_me, featured, testimonial, preferred, work_experience, rep_matters, speaking_engagements, current_position, additional_fields, lat, lon, post_title, post_caption, post_category, post_image, post_price, post_tags, group_category, property_status, property_type, property_beds, property_baths, property_price
This is because they will have a conflict between each other.