Congratulations on becoming a New Page Reviewer. Reviewing is the one of the most important single maintenance tasks on the whole site. It's what keeps bad pages out, and equally important, it gives a boost to new, good faith users creating their first genuine articles. Reviewing new pages needs a thorough knowledge of deletion and notability guidelines.
New Page Review is a vital function as the front line of interaction between new authors and community members devoted to policing the quality of the project. It has a variety of detailed, quite complex possible actions for patrolling pages in all namespaces. Only New Page Reviewers can mark pages as 'Reviewed' or 'Patrolled' which releases them for indexing by search engines. Any reviewing action done through the page curation toolbar by a reviewer marks an article as reviewed (adding maintenance tags, nominating for deletion, etc.). If you don't want the article marked as reviewed, you can unreview it by opening the review panel and clicking "Mark as unreviewed".
If you are new to New Page Reviewing, it is essential that you also read Page Curation Help, view its video tour and read WP:FIELD. Reviewing needs a near-admin knowledge of deletion and notability policies.
It is important to review correctly and seriously. The sheer volume of articles created is immense. Even a few percentage points more of erroneous or bitey reviewing can adversely affect hundreds of articles or deter many new users a day. It is critical that editors don't review sloppily nor treat it as a game or contest.
Reviewing is entirely voluntary and carries no obligation.
Tools such as Huggle and Stiki are specifically designed for counter-vandalism and are fine for vandalism patrollers; they should never be used for reviewing new pages.
If you have a question or concern, post a message at the New pages patrol noticeboard, and an experienced reviewer or editor will be along soon to help you. For other help using the tools, see the related tabs above.