The Nautical Almanac is a publication containing detailed information about the positions of the Moon, sun, planets, and stars, plus a number of tables used in common calculations.
See Wikipedia article and vinamaso.net for more information about the format of the almanac.
The key elements of the Nautical almanac are:
Provides a table to correct for dip error (due to the curvature of the earth) and tables to correct for atmospheric refraction and semidiameter for the sun, planets, and stars. (Lunar corrections are at the end of the book.)
The bulk of the book consists of pages of almanac data. Each two-page spread covers three days. The GHA and declination of Aries, several planets, the sun, and the Moon. The SHA and declination of several key stars is also given.
Other values, given for interpolation purposes, are d and v.
The value d is the hourly change in declination of the object. This value is given as an unsigned number, so you need to compare two adjacent lines in the almanac to determine its sign. d is given at the bottom of the page for most objects. It changes very rapidly for the Moon, however, and so it's given in the column data directly.
The value v is the difference in the nominal hourly change in GHA of the object. This value is given as a signed number, which is added to a base value taken from the Increments and Corrections tables at the end of the book. Again, this is given at the bottom of the page for the Sun and planets, and directly in the column for the Moon.
SD is the semidiameter of the object, used to correct for measurements made relative to the object's limb. The altitude correction tables already include corrections for the Sun, but not for the Moon. Because the Moon's semidiameter changes relatively quickly, three values (one for each day on the page) are given at the bottom of the page.
HP is Horizontal Parallax. It is given in the column data for the Moon, and can exceed a degree in magnitude.
Data for stars is given directly in SHA and Declination. These values change very slowly, and you can span several pages in the almanac without seeing any changes.
See The Online Nautical Almanac for computer-generated pages similar to those found in the printed almanac.