This lecture introduces expressions and operators in C++, explaining how to assign values, use literals, and apply arithmetic operators. It covers the types of literals, common operators like +, -, *, /, and special operators such as %, ++, and --. The division between int values and the use of +=, ==, *=, and / are also discussed. Additionally, it explores the challenges of assigning decimal values to integer variables, the concept of integer division, and solutions to avoid losing precision. The lecture concludes with an overview of mathematical functions provided by the C++ standard library, including trigonometric functions, exponential functions, logarithmic functions, and constants like PI and e.