Because web hosting services host websites belonging to their customers, online security is an important concern. When a customer agrees to use a web hosting service, they are relinquishing control of the security of their site to the company that is hosting the site. The level of security that a web hosting service offers is extremely important to a prospective customer and can be a major consideration when considering which provider a customer may choose.
A handful of domains will have restrictions on them, which means you can only purchase them if you meet or exceed certain criteria or have authorization (some examples are .gov, .edu and .mil). But most extensions are available to everyone. In fact, most country code Top Level Domains (ccTLDs) are available for anyone to purchase, even if you don't reside in the country code in question.
Note: The dual meanings "host"/"guest" of Latin hospes and its progeny are due to customs of reciprocity: a person serving as guest on one occasion would act—and be expected to act—as host on another occasion to a visiting former host. Both Latin hospes and Slavic gospodĭ have undergone a considerable degree of phonetic reduction from their putative etymons—in particular in the Slavic case, where Latin unstressed syllable reduction and syncope were not at play—leading some to question the correctness of the etymologies. Parallel compounds with the same second element are Greek despótēs "master, lord" (going back to *dems-pot- "master of the house"; see despot), Sanskrit dámpatiḥ "householder, lord of the house," Avestan də̄ṇg paitiš; Sanskrit viśpátiḥ "chief of a settlement/tribe," Avestan vīspaitiš, Lithuanian viẽšpats "lord" (with outcomes of Indo-European *u̯iḱ-, *u̯oiḱ- "house, community"; see vicinity).