A swing state is typically a U.S. state whose votes are neither reliably Democratic nor reliably Republican in a given election, making its outcome "up for grabs" or unpredictable until the voting is complete. These states are often called battleground, toss-up, or purple states because their political leanings can shift between elections. Key points about swing states:

• Color associations: In common political shorthand, states that lean Republican are colored red, those that lean Democratic are blue, and battleground states that could go either way are often referred to as purple (mixtures of red and blue). This color convention is widely used in media coverage of elections, though it is a simplification of more complex voting patterns.
• Why they matter: Because electoral outcomes hinge on those few competitive states, campaigns concentrate resources, advertising, and candidate visits there to sway voters.
• Examples: The specific list of swing states changes over time with demographics and political trends, but states frequently cited in recent cycles include places like Pennsylvania, Michigan, Wisconsin, Arizona, Georgia, Nevada, North Carolina, and others depending on the election year.

If you’d like, I can tailor the explanation to a particular election year or explain how swing-state status is determined (e.g., polling volatility, past voting patterns, and margins of victory).