C++ regex difference between regex_search and regex_match

regex_cpp.cpp

#include <regex>
#include <iostream>
#include <string>

using namespace std;

class RegExpSearch {
public:
    static std::smatch check_string(const std::regex &re, const std::string &s) {
        std::smatch matches;
        
        std::regex_search(s, matches, re);
        
        return matches;
    }
};

class RegExpMatch {
public:
    static std::smatch check_string(const std::regex &re, const std::string &s) {
        std::smatch matches;
        
        std::regex_match(s, matches, re);
        
        return matches;
    }
};

int main() {
    string user_pattern;
    regex pattern;
    
    cout << "enter the pattern: ";
    getline(cin, user_pattern);
    
    try {
        pattern = user_pattern;
    }
    catch (std::regex_error &e) {
        cout << user_pattern << " is a wrong pattern" << endl;
        
        return 1;
    }
    
    cout << "enter lines to search in: ";
    
    for (string line; getline(cin, line); ) {
        // Change here the RegExpSearch to RegExpMatch and vice versa to understand the difference
        auto m = RegExpSearch::check_string(pattern, line);
        
        if (!m.empty()) {
            for (auto i = 0; i < m.size(); ++i) {
                cout << "match[" << i << "]: " << m[i] << endl;
            }
        }
        else {
            cout << "didn't match" << endl;
        }
    }
    
    return 0;
}