像there i sat,there i am这种句子属于什么类型的句子?包含什么语法知识点?

像there i sat,there i am这种句子属于什么类型的句子?包含什么语法知识点?
英语渣渣一枚,求懂的人详解.

there be 句型
一、构成：There be ...句型表示的是 “某处有(存在)某人或某物”,其结构为There be(is,are,was,were )+名词+地点状语.例如：
There are fifty-two students in our class.
There is a pencil in my pencil-case.
There was an old house by the river five years ago.
二、各种句式：
否定句：There be句型否定句式的构成和含有be动词的其它句型一样,在be后加上“not”.也可用“no”来表示.即：no + n.（名词）= not a\an\any + n.（名词）.注意：no + n.（可数名词单数）= not a\an + n.（可数名词单数）；no + n.（可数名词复数）= not any + n.（可数名词复数）；no + n.（不可数名词）= not any + n.（不可数名词）.例如：
There is an orange in her bag.
→There isn’t an orange in her bag.
→There is no orange in her bag.
There are some oranges in her bag.
→There aren’t any oranges in her bag.
→There are no oranges in her bag.
一般疑问句：There be结构的一般疑问句变化只需把be动词移到句首,再在句尾加上问号即可.例如：
There is some money in her handbag.
→ Is there any money in her handbag?(疑问句和否定句中,some改为any,something改为anything.)
There is something new in today’s newspaper.
→There isn’t anything new in today’s newspaper.
→Is there anything new in today’s newspaper?
特殊疑问句：
There be句型的特殊疑问句有以下三种形式：
① 对主语提问：当主语是人时,用 “Who’s + 介词短语?”；当主语是物时,用 “What’s + 介词短语?”.其中there在口语中常常省略.注意：无论原句的主语是单数还是复数,对其提问时一般都用be的单数形式(回答时却要根据实际情况来决定).如：
There is a bird in the tree.→What’s in the tree?
There are some bikes over there.→What’s over there?
There is a little girl in the room.→Who is in the room?
② 对地点状语提问：用 “Where is \ are + 主语?”表示（注意其答语变化）：例如：
There is a computer in my office.
→ Where is the computer?----It’s in my office.
There are four children in the classroom.
→Where are the four children?—They’ re in the classroom.
③ 对数量提问：一般有两种提问方式：
如果主语是可数名词,无论是单数还是复数,都用“How many +可数名词复数+ are there + 介词短语?”表示：
There are twelve months in a year.
→How many months are there in a year?
There is only one book in my bag.
→ How many books are there in your bag?
There is a cat in the box.
→ How many cats are there in the box?
如果主语是不可数名词,则用“ How much + 不可数名词 + is there + 介词短语?”表示：
There is some money in my purse.How much money is there in
your purse?
反意疑问句：There be或There加其它动词,其反意疑问句一律用…there?例如：
There is a beautiful girl in the garden,isn’t there?
There used to be no school here,used there \did there?
三、注意事项：
1.There be句型中be动词的形式要和其后的主语在人称和数上保持一致.
如果句子的主语是单数的可数名词,或是不可数名词,be动词用“is”“was”.例如：
There is a basketball in the box.
There is a little milk in the glass.
如果句子的主语是复数名词,be动词就用“are” “were”.例如：
There are many birds in the tree.
There were many people in the street yesterday.
如果有两个或两个以上的名词作主语,be动词要和最靠近它的那个主语在数上保持一致,也就是我们常说的 “就近原则”.例如：
There is an orange and some bananas in the basket.
There are some bananas and an orange in the basket.
2.There与be中间可插入一些表推测的情态动词、表时态的短语和一些动词短语 (如和将来时be going to\ will、现在完成时 have\has + pp.、used to结构等连用,注意其构成形式,这一内容在我们日常练习中经常出现错误,是一难点,也是历年中考试题中的一个考点.).例如：
There must be a pen in the box.
3.There be句型和have\has的区别：
There be句型表示 “存在有”,have\has表示 “拥有” “所有”,两者不能同时使用.例如：
桌子上有三本书.There are three books on the desk.
我有三本书.I have three books.
4.There be + 主语 + doing +介词短语.例如：
There is a truck collecting rubish outside.
There is a wallet lying on the ground.