What is the relationship between Bitcoin and tether?

Could you elaborate on the interplay and potential correlations between Bitcoin, the world's first and most well-known cryptocurrency, and Tether, a blockchain-enabled platform that aims to facilitate the issuance of stablecoins? Do they compete in the same market space, or are they complementary in terms of their functionality and usage? Furthermore, how does the price stability of Tether's USDT stablecoin, which is pegged to the US dollar, influence the volatility of Bitcoin's price? Is there a significant correlation between the two, and if so, how does it manifest itself in the market?