The image contains two mathematical symbols or notations:

1. $\{x \mid x \in \mathbb{R}\}$:

   • This represents the set of all real numbers ($x$).
   • It is a set-builder notation which reads as "the set of all $x$ such that $x$ is an element of the set of real numbers ($\mathbb{R}$)."
   • In simpler terms, this defines the set of all real numbers, which is the set of all possible numbers on the continuous number line, including both rational and irrational numbers.

2. $\varnothing$ (Empty set symbol):

   • This symbol represents the empty set, which is a set containing no elements.
   • The empty set is a fundamental concept in set theory, denoting a set with zero members.

Would you like any further clarifications on these concepts?

Here are 5 related questions you might find helpful:

1. How is set-builder notation used in more complex set definitions?
2. Can you provide examples of sets other than $\mathbb{R}$ (real numbers)?
3. What is the difference between the empty set ($\varnothing$) and the set containing zero ($\{0\}$)?
4. Are there any other notations for describing sets of numbers?
5. How are empty sets used in mathematical proofs or logic?

Tip: The empty set ($\varnothing$) is always a subset of every set, including itself.