psql \d

 \d <table> describe table (or view, index, sequence)
 \d{t|i|s|v}    list tables/indices/sequences/views
 \d{p|S|l}      list permissions/system tables/lobjects
 \da            list aggregates
 \dd [object]   list comment for table, type, function, or operator
 \df            list functions
 \do            list operators
 \dT            list data types