Attitudes toward public affection form a clear global gradient. At the relaxed end, Western Europe, Latin America, and North America treat hand-holding and kissing in public as unremarkable. In the middle, East Asia and much of Southeast Asia accept hand-holding but consider kissing in public embarrassing rather than offensive. At the conservative end, across parts of the Middle East, South Asia, and North Africa, couples showing affection publicly face social disapproval, and a small number of countries treat it as a legal matter, particularly for unmarried couples; for those destinations, check your government's travel advisory and local guidance from official sources before you go, since the rules and their enforcement vary.
Two nuances catch visitors out. First, same-gender friends holding hands or linking arms is ordinary friendship in parts of South Asia, the Middle East, and Africa, and means nothing romantic, while in those same places opposite-gender contact is what draws attention. Second, LGBTQ travellers face a separate and more serious legal landscape in some countries, which deserves specific research through official channels rather than assumptions in either direction.
The practical rule: observe what local couples of your age do in public and stay a notch more reserved than that, keeping anything beyond hand-holding for private settings in conservative regions. Discretion costs little and prevents both awkwardness and genuine trouble.