The IRS website Retirement Plans section describes technical assistance "an informal process where a written request is made to Technical Review or Area Counsel for technical assistance. Area Counsel will provide an interpretation of law. The Review Staff can advise and assist IRS agents and managers on technical and procedural issues."
Written responses can be very informal. Generally, they set forth the basics of the law without applying the law to a specific set of facts. The National Office is instructed to be very cautious in its use of technical assistance, so as not to infringe on the taxpayer's rights as set forth in the Rev. Proc. 2016-2 for technical advice. See the Technical Advice Memorandum section of this libguide.
Unlike technical advice memoranda, written technical assistance to IRS agents historically has not been released for publication. The Internal Revenue Manual provides restrictive guidelines as to releasing legal advice to the public.