This website is used when you are making frequent contact with potential clients, following leads, dealing with referrals and otherwise using alternative means to generate business. Your website it used primarily to validate your credentials. Clients do not expect there to be significant information but, depending on your business, pictures always help the sale.
This type of website does a deeper dive into your knowledge, skills and professional competency than a simple brochure site. There will be more text, examples of completed projects, testimonials from satisfied clients and all the information that a potential client might use to make a decision. This is still a brochure site since there is no direct commerce.
This website goes into the most detail on the service level provided by your company as a way to stand out among a large pool of specialists.
This type of site is best in saturated industries with many competitors. What makes you stand out might not be just the level of service, but how you approach your clients issues, unusual talents you bring to the market, geographic area served or any number of differentiators.