A vertical portal is a unique access point to a certain industry, market niche, or area of interest.
It is the opposite of a horizontal portal where the listed sites cover an extensive array of subjects. Vertical portals, in contrast, deal with limited subjects, addressing just a single topic or a single type of topic, such as insurance, health care, automobiles, food manufacturing, etc.
A vertical portal is also known as a vortal.
Techopedia explains Vertical Portal
A vertical industry targets a comparatively narrow range of services and products, whereas a horizontal industry aims at producing a wide variety of services or products.
Since most industries tend to specialize, they are likely to be vertical. A term that may also be used is interest community website because any vertical industry draws together people who share an interest in selling, buying, or exchanging information regarding that specific industry.
The vertical portals are also considered probable business-to-business (B2B) communities. For instance, small business persons using work-from-home options may very well be interested in an extensive vertical portal that provides ideas and/or product information on how to set up and maintain a home office.
Search engines such as Yahoo! are horizontal portals as they aim to catch the attention of users worldwide, not limited to a special niche. However, for each Yahoo! on the web, there are virtually countless vertical portals. These portals are fundamentally online communities in which those people looking for a certain topic can meet up online.
It is essential to understand that there are normally multiple vertical portals for any given subject. At times, based on the subject matter, there may be thousands of vertical portals on the same topic or niche.
Some examples of vertical portals include:
www.contractor.com - a vertical portal for the construction industry
www.shotgunsports.com - for shooting sports community