hibernate 中的Query Language

1
"select blog.id, blog.name, count(blogItem) " +
"from Blog as blog " +
"left outer join blog.items as blogItem " +
"group by blog.id " +
"order by max(blogItem.datetime)

2
"from Blog as blog " +
"left outer join fetch blog.items " +
"where blog.id = :blogid"

不太理解hibernate 中的Query Language

比如1中的 Blog，blog.items...是数据库中的表呢 还是实列对象
在使用关联的时候 他们又是通过什么关联的呢 是怎么体现的

2中的left outer join fetch这种关联是什么意思啊

还有我看到 hibernate的文档上还有
from eg.Cat as cat
inner join cat.mate as mate
left outer join cat.kittens as kitten

不懂 谁能解释一下