The document discusses oblique asymptotes, which are lines that a graph approaches but does not touch. Oblique asymptotes occur when the degree of the highest-order term in the denominator of a rational function is greater than the degree of the highest-order term in the numerator. The slope of an oblique asymptote is determined by taking the limit of the ratio of the highest-order terms in the numerator and denominator as the variable approaches plus or minus infinity.