Hello gurus, I would like to get deep into charset and encoding isse, also tried google it but no luck. Please see bellow

My configuration

[pista@HP-PC MULTIBOOT]$ locale
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

[pista@HP-PC konvertovanie]$ cat file1 
- Prich�dzaj�.
- Kto prich�dza?
N�� svet okupuj
vyvinut� �udsk� druhy,

[pista@HP-PC konvertovanie]$ less file1 
- Prich<E1>dzaj<FA>.
- Kto prich<E1>dza?
N<E1><9A> svet okupuj<FA>
vyvinut<E9> <BE>udsk<E9> druhy,

[pista@HP-PC konvertovanie]$ vi file1 
- Prichádzajú.
- Kto prichádza?
Ná<9a> svet okupujú
vyvinuté ¾udské druhy,

[pista@HP-PC konvertovanie]$ iconv -f WINDOWS-1250 -t UTF-8 file1
- Prichádzajú.
- Kto prichádza?
Náš svet okupujú
vyvinuté ľudské druhy,

[pista@HP-PC konvertovanie]$ cat file1 | od -An -t dC -c
   45   32   80  114  105   99  104  -31  100  122   97  106   -6   46   13   10
    -         P    r    i    c    h  341    d    z    a    j  372    .   \r   \n
   45   32   75  116  111   32  112  114  105   99  104  -31  100  122   97   63
    -         K    t    o         p    r    i    c    h  341    d    z    a    ?
   13   10   78  -31 -102   32  115  118  101  116   32  111  107  117  112  117
   \r   \n    N  341  232         s    v    e    t         o    k    u    p    u
  106   -6   13   10   48   48   58   48   48   58   48   53   44   56   50   48
    j  372   \r   \n    0    0    :    0    0    :    0    5    ,    8    2    0
   32   45   45   62   32   48   48   58   48   48   58   48   55   44   54   53
         -    -    >         0    0    :    0    0    :    0    7    ,    6    5
   52   13   10  118  121  118  105  110  117  116  -23   32  -66  117  100  115
    4   \r   \n    v    y    v    i    n    u    t  351       276    u    d    s
  107  -23   32  100  114  117  104  121   44   13   10
    k  351         d    r    u    h    y    ,   \r   \n

[pista@HP-PC konvertovanie]$ file -bi file1 
text/plain; charset=unknown-8bit
[pista@HP-PC konvertovanie]$ iconv -f WINDOWS-1250 -t UTF-8 file1 > file1.utf8
[pista@HP-PC konvertovanie]$ file -bi file1.utf8 
text/plain; charset=utf-8

Most of the websites you referenced are not really applicable to this question. By convention, using LANG=en_US.UTF-8 indicates that you are using the English language with formatting conventions used in the United States encoded using the UTF-8 character set.

The UTF-8 character set encodes over a million characters using one to six bytes to encode a character. Any byte that has the high order bit set is part of a multi-byte character. Any byte that has the high order bit clear represents the same character as the US-ASCII character with the same value. See Wikipedia UTF-8 for details.

The Windows-1250 codeset is used to represent text for Central and Eastern European characters using Latin script and encodes 251 characters using one byte to encode a character. Any byte that has the high order bit clear represents the same character as the US-ASCII character with the same value. See Wikipedia Windows-1250 for details. That web page shows that the character with decimal value 251 in Windows-1250 ("á") corresponds to the Unicode character with value 00E1 which is encoded in UTF-8 as the two byte sequence 0xC3 0xA1 (or in decimal 195 161). Since you can see that the single byte with value 251 (base 10) in Windows-1250 is not the same as the two byte values 195 followed by 161 in UTF-8, you will not see the same printed characters when you try to look at Windows-1250 codeset characters when you tell the system that you are using a locale with a UTF-8 codeset representation of characters. Furthermore, in UTF-8 there is never a single byte character with the high bit set and there is never a multi-byte character than has any byte without the high bit set.

The iconv utility knows how to convert characters from one codeset to another codeset and as you have seen does so successfully. But, expecting characters from a single byte codeset with the high bit set to be magically converted from invalid characters in UTF-8 based on an unspecified assumption that invalid UTF-8 characters should be treated as Windows-1250 characters just won't work.