Strict and Partial Orders

What is the definition of a Partial Order, a Strict Order, and a Total Order?
Are the following partial orders, strict orders, or neither? If they are an order, are they a total order?
- Geographic containment:
  - $S=$ The set of all geographic areas.
  - $\forall a,b \in S$ , $a ≤ b$ if $a$ is contained within $b$
- Company Hierarchy (If we are referring to strict boss -> employee relationships):
  - $S=$ The set of all employees of a company.
  - $\forall a,b \in S$ , $a < b$ iff $b$ directly manages $a$
- Lexicographic Order (also known as Alphabetical Order):
  - $\forall $a,b$,$c,d$ \in S$ x $N$ , $(a,b) \leq (c,d)$ iff $(a < c)$ or $(a = c$ and $b \leq d).$
  - You can assume $S$ and $N$ have valid partial orders.
What is the relationship between partial/strict orders and directed acyclic graphs?
Draw the graph for the relation “a divides b” for the first 15 natural numbers. Is this a partial order? If so, are all elements comparable?
Find a topological sort for this graph. What are the minimal and maximal elements?