The object database contains objects of three main types: blobs, which
hold file data; trees, which point to blobs and other trees to build up
-directory heirarchies; and commits, which each reference a single tree
+directory hierarchies; and commits, which each reference a single tree
and some number of parent commits.
The commit, equivalent to what other systems call a "changeset" or
Named pointers called refs mark interesting points in history. A ref
may contain the SHA1 name of an object or the name of another ref. Refs
with names beginning `ref/head/` contain the SHA1 name of the most
-recent commit (or "head") of a branch under developement. SHA1 names of
+recent commit (or "head") of a branch under development. SHA1 names of
tags of interest are stored under `ref/tags/`. A special ref named
`HEAD` contains the name of the currently checked-out branch.